Coil helper air suspensions employ an airbag fitted inside a coil spring. The coil spring is generally fitted closely to the airbag and consequently the airbag is prone to wear from rubbing against the coil spring.
It has been proposed to incorporate some form of protective integral outer cover or layer to protect the airbag from this rubbing by the coil spring. Examples of suspensions with some form of protective layer or insert are in the following patents specifications by country code, the disclosures of which are incorporated herein by reference in their entirety (the disclosure herein is not an admission that any of these are common general knowledge):                CN203623313U, DE102006016141A1, US2016178024A1, U.S. Pat. Nos. 3,897,941A, 4,894,108A, 6,145,879.        